Spectrometers are applied for investigation of substances or of measured objects, wherein spectral fractions of different wavelengths are registered as spectrometric data and examined. The spectral ranges and corresponding wavelengths of the spectral fractions of a substance to be examined can, in such case, vary across a relatively large wavelength range. The spectrometers register the spectral fractions of different wavelengths as a function of their respective intensities, from which deductions concerning the composition of the investigated substance can be made.
The present invention is concerned with the calibrating of such spectrometers. In the state of the art, it is known, on the one hand, to conduct a calibrating of spectrometers or spectral apparatuses by mechanical corrections and adjustments to the apparatus itself. Thus, for example, in WO/2003/067204, a calibrating of echelle-spectrometers is described, in the case of which, through adjustment of the slit width of an intermediate slit arrangement, a calibrating of a pre-chromator to its desired position occurs.
Furthermore, it is known in the state of the art to perform the calibrating of measured spectra and associated substance concentrations of the measured object on the level of the spectrometric data: if chemometrics are selected, for example, from a plurality of measured spectral fractions those spectral fractions physically relevant for the particular measurement object are considered, and by means of this selection, a calibrating of the spectrometric apparatus is performed. The known calibration methods with selection of relevant spectral fractions from the total measured spectrum of the spectrometric data most often used, in such case, iterative algorithms are employed, in order to calculate main components from a matrix composed of the intensities of the measured spectra. In the context of calibrating of spectrometers previously used for this purpose, for example, mathematical methods such as the “partial least squares method” (PLS method for short), or similar such iterative algorithms. These estimation methods serve the purpose of providing a solution for the so-called minimizing problem in the case of under-determined systems of equations. Disadvantageous in the case of the known methods for minimizing the measured data set such as the PLS method is, however, that, for the selection of particular physically relevant spectral fractions from the totality of measured wavelengths, recourse to expert knowledge is always necessary. Only a “manual” selection by bringing in a specialist concerned with spectrometric measuring allows the performance of a calibrating of spectrometric data by means of such iterative known algorithms. The known methods for calibrating are, consequently, cost and time intensive and can vary in their calibration quality, depending on the particular expert. The previously necessary bringing in of an expert or expert system is based, moreover, on an estimation methodology which can easily lead to errors in the calibrating of the data.